JP7701167B2 - solid state battery - Google Patents

Description

The present invention relates to a solid-state battery.

In recent years, technology has been proposed for solid-state batteries that use solid electrolytes, which have high energy density and are highly safe against heat. When solid-state batteries are used for applications that require high current and high voltage, such as for driving the motors of electric vehicles and hybrid electric vehicles, solid-state batteries that are modularized by combining multiple single cells are used.

Patent Document 1 discloses a configuration in which a laminated body constituting a solid-state battery is housed in a laminate film as an exterior body, and multiple laminated solid-state batteries are combined to form a battery module.

Patent Document 2 also discloses a method for producing a solid-state battery, in which a laminate is formed by stacking, in this order, a positive electrode layer having a positive electrode current collector and a positive electrode active material, a solid electrolyte layer, and a negative electrode layer having a negative electrode active material layer and a negative electrode current collector, and pressing the laminate.

JP 2019-102261 A JP 2020-061258 A

The solid-state battery described in Patent Document 1 is fixed by applying pressure to multiple solid-state batteries by sandwiching them between plates. However, simply pressing a multi-layered cell of solid-state batteries with high pressure may cause the electrode layers of each solid-state battery to short circuit or be destroyed by the rolling.

In addition, when the method for manufacturing a solid-state battery described in Patent Document 2 is applied to the manufacture of solid-state batteries, a huge number of laminates must be individually pressed and then laminated in a predetermined number, and these steps become a bottleneck, resulting in a problem of not being able to increase manufacturing capacity.

The present invention has been made in consideration of the above, and aims to provide a solid-state battery that can suppress short circuits and breakdowns due to rolling in the electrode layers of each laminate when the laminate is stacked and then subjected to high-pressure pressing.

(1) In order to achieve the above object, the present invention provides a solid-state battery comprising a laminate in which a positive electrode current collector, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector are laminated in this order, and a conductive rigid body made of a conductive rigid body, in which the laminate and the conductive rigid body are alternately laminated and the conductive rigid body is disposed on both outermost sides in the stacking direction.

(2) The present invention also provides a solid-state battery comprising an assembly formed by stacking a pair of laminates, each of which is formed by stacking a positive electrode collector, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode collector in this order, so that the positive electrode collectors are in contact with each other, and a conductive rigid body formed of a conductive rigid body, in which the assembly and the conductive rigid body are alternately stacked and the conductive rigid body is disposed on both outermost sides in the stacking direction.

(3) In the solid-state battery of (1) or (2), the end of the positive electrode active material layer in the planar direction may be disposed inward in the planar direction relative to the end of the adjacent solid electrolyte layer in the planar direction.

(4) In any one of the solid-state batteries (1) to (3), an insulating spacer may be further provided on the outer side of the positive electrode active material layer in the planar direction.

The present invention provides a solid-state battery that can suppress short circuits and breakdowns caused by rolling in the electrode layers of each laminate when the laminate is stacked and then subjected to a high-pressure press process.

FIG. 1 is an exploded cross-sectional view of a solid-state battery according to a first embodiment of the present invention. FIG. 4 is an exploded cross-sectional view of a solid-state battery according to a second embodiment of the present invention. FIG. 11 is an exploded cross-sectional view of a solid-state battery according to a third embodiment of the present invention. FIG. 11 is an exploded cross-sectional view of a solid-state battery according to a fourth embodiment of the present invention. FIG. 1 is an exploded cross-sectional view of a conventional solid-state battery. FIG. 1 is an exploded cross-sectional view of a conventional solid-state battery.

First Embodiment
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. However, the embodiment described below is merely an example of the present embodiment, and the present invention is not limited to the following.

[Solid battery]
Fig. 1 is an exploded cross-sectional view showing the configuration of a solid-state battery 101 according to a first embodiment of the present invention. The solid-state battery 101 according to this embodiment includes a plurality of laminates 11 and a plurality of conductive rigid bodies 6 made of conductive rigid bodies. As shown in Fig. 1, the solid-state battery 101 has the laminates 11 and the conductive rigid bodies 6 alternately laminated, and the conductive rigid bodies 6 are disposed on both outermost sides in the stacking direction. That is, the solid-state battery 101 is produced by stacking the laminates 11 sandwiched between the conductive rigid bodies 6 and then compressing them.

(Laminate)
The laminate 11 according to this embodiment is formed by laminating, in this order, a positive electrode current collector 1, a positive electrode active material layer 2, a solid electrolyte layer 3, a negative electrode active material layer 4, and a negative electrode current collector 5. The positive electrode layer of the laminate 11 is formed by the positive electrode current collector 1 and the positive electrode active material layer 2, and the negative electrode layer is formed by the negative electrode active material layer 4 and the negative electrode current collector 5.

(Positive electrode layer)
The positive electrode layer is a layer consisting of a positive electrode active material layer 2 containing at least a positive electrode active material, and a positive electrode current collector 1. As the positive electrode active material, a material capable of releasing and absorbing a charge transfer medium may be appropriately selected and used. From the viewpoint of improving the conductivity of the charge transfer medium, a solid electrolyte may be optionally contained. In addition, a conductive assistant may be optionally contained in order to improve the conductivity. Furthermore, from the viewpoint of expressing flexibility, etc., a binder may be optionally contained. As for the solid electrolyte, the conductive assistant, and the binder, those generally used in solid batteries can be used.

The positive electrode active material may be the same as that used in the positive electrode layer of a general solid-state battery, and is not particularly limited. For example, in the case of a lithium ion battery, a layered active material containing lithium, a spinel type active material, an olivine type active material, etc. may be mentioned. Specific examples of the positive electrode active material include lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), LiNi _p Mn _{q Cor} O ₂ (p+q+r=1), LiNi _p Al _{q Cor} O ₂ (p+q+r=1), lithium manganate (LiMn ₂ O ₄ ), a different element substituted Li-Mn spinel represented by Li ₁ +xMn ₂ -x-yMyO ₄ (x+y=2, M=at least one selected from Al, Mg, Co, Fe, Ni, and Zn), lithium titanate (oxide containing Li and Ti), and lithium metal phosphate (LiMPO ₄ , M=at least one selected from Fe, Mn, Co, and Ni).

The positive electrode current collector 1 is not particularly limited as long as it has the function of collecting current from the positive electrode layer, and examples thereof include aluminum, aluminum alloys, stainless steel, nickel, iron, and titanium, among which aluminum, aluminum alloys, and stainless steel are preferred. In addition, examples of the shape of the positive electrode current collector include foil and plate shapes.

In the laminate 11 according to this embodiment, it is preferable that the end of the positive electrode active material layer 2 in the planar direction is disposed more inward in the planar direction than the end of the adjacent solid electrolyte layer 3 in the planar direction. This makes it possible to more reliably suppress short circuits.

(Solid electrolyte layer)
The solid electrolyte layer 3 is a layer laminated between the positive electrode layer and the negative electrode layer, and contains at least a solid electrolyte material. Charge transfer medium conduction between the positive electrode active material and the negative electrode active material can be performed via the solid electrolyte material contained in the solid electrolyte layer.

The solid electrolyte material is not particularly limited as long as it has charge transfer medium conductivity, but examples include sulfide solid electrolyte materials, oxide solid electrolyte materials, nitride solid electrolyte materials, and halide solid electrolyte materials. Among these, sulfide solid electrolyte materials are preferred because they have higher charge transfer medium conductivity than oxide solid electrolyte materials.

Examples of sulfide solid electrolyte materials for lithium ion batteries include Li ₂ S-P ₂ S ₅ and Li ₂ S-P ₂ S ₅ -LiI. The above description of "Li ₂ S-P ₂ S ₅ " means a sulfide solid electrolyte material obtained by using a raw material composition containing Li ₂ S and P ₂ S ₅ , and the same applies to other descriptions.

On the other hand, examples of oxide solid electrolyte materials include, for example, NASICON type oxides, garnet type oxides, and perovskite type oxides in the case of lithium ion batteries. Examples of NASICON type oxides include oxides containing Li, _Al , Ti, P, and O (e.g., _{Li1.5Al0.5Ti1.5} ( _PO4 ) ₃ ). Examples of garnet type oxides include oxides containing Li, La, Zr, and _O (e.g., _Li7La3Zr2O12 ). Examples of perovskite type oxides include oxides containing Li _, La, Ti, _{and O} (e.g., _LiLaTiO3 ).

(Negative electrode layer)
The negative electrode layer is a layer consisting of a negative electrode active material layer 4 containing at least a negative electrode active material, and a negative electrode current collector 5. From the viewpoint of improving the charge transfer medium conductivity, a solid electrolyte may be optionally contained. In addition, a conductive assistant may be optionally contained in order to improve the electrical conductivity. Furthermore, from the viewpoint of expressing flexibility, etc., a binder may be optionally contained. As for the solid electrolyte, the conductive assistant, and the binder, those generally used in solid-state batteries can be used.

The negative electrode active material is not particularly limited as long as it can absorb and release a charge transfer medium, and for example, in the case of a lithium ion battery, examples of the material include lithium transition metal oxides such as lithium titanate (Li ₄ Ti ₅ O ₁₂ ), transition metal oxides such as TiO ₂ , Nb ₂ O ₃ and WO ₃ , metal sulfides, metal nitrides, carbon materials such as graphite, soft carbon and hard carbon, metallic lithium, metallic indium and lithium alloys, etc. The negative electrode active material may be in the form of a powder or a thin film.

The negative electrode current collector 5 is not particularly limited as long as it has the function of collecting current from the negative electrode layer. Examples of materials for the negative electrode current collector include nickel, copper, and stainless steel. Examples of the shape of the negative electrode current collector include foil and plate shapes.

(Conductive rigid body)
A plurality of conductive rigid bodies 6 are used to sandwich the plurality of laminates 11. Furthermore, by using a material having electrical conductivity as the conductive rigid bodies 6, the plurality of laminates 11 are electrically connected by the conductive rigid bodies 6. By alternately stacking the laminates 11 and the conductive rigid bodies 6 and arranging the conductive rigid bodies 6 on both outermost sides in the stacking direction, it is possible to suppress short circuits and breakdowns due to rolling in the electrode layers (positive electrode layer, negative electrode layer) of the individual laminates 11 when the solid-state battery 101 is pressed.

The material of the conductive rigid body 6 is not particularly limited as long as it is a material having electrical conductivity, but is preferably a metal material, and particularly preferably stainless steel (SUS). The size of the conductive rigid body 6 is preferably such that the length in the surface direction is greater than the electrode layer of the laminate 11 that faces the conductive rigid body 6. The thickness of the conductive rigid body 6 is preferably several hundred μm.

[Manufacturing method]
The following describes a method for manufacturing the solid-state battery 101 according to this embodiment. However, the solid-state battery 101 according to this embodiment can be manufactured with appropriate modifications within the scope of the object of the present invention.

(Method of manufacturing the positive electrode layer)
A positive electrode layer can be manufactured by disposing a positive electrode mixture containing a positive electrode active material on the surface of a positive electrode current collector 1. A method similar to that used in the past can be used to manufacture the positive electrode layer, and the positive electrode can be manufactured by either a wet method or a dry method. Hereinafter, a case where a positive electrode is manufactured by a wet method will be described.

The positive electrode layer is manufactured by a process of obtaining a positive electrode mixture paste containing a positive electrode mixture and a solvent, and a process of applying the positive electrode mixture paste to the surface of the positive electrode current collector 1 and drying it to form a positive electrode active material layer 2 on the surface of the positive electrode current collector 1. For example, the positive electrode mixture paste is obtained by mixing and dispersing the positive electrode mixture in a solvent. The solvent used in this case is not particularly limited, and may be appropriately selected depending on the properties of the positive electrode active material, solid electrolyte, etc. For example, a non-polar solvent such as heptane is preferable. Various mixing and dispersing devices such as an ultrasonic dispersing device, a shaker, and Filmix (registered trademark) can be used to mix and disperse the positive electrode mixture and the solvent. The solid content of the positive electrode mixture paste is not particularly limited.

The positive electrode mixture paste thus obtained is applied to the surface of the positive electrode collector 1 and dried to form the positive electrode active material layer 2 on the surface of the positive electrode collector 1, thereby obtaining a positive electrode layer. A known application means such as a doctor blade may be used as a means for applying the positive electrode paste to the surface of the positive electrode collector 1. The total thickness of the positive electrode active material layer 2 and the positive electrode collector 1 after drying (thickness of the positive electrode) is not particularly limited, but is preferably 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 100 μm or less, from the viewpoint of energy density and lamination, for example. The positive electrode may also be produced through an optional pressing process. The positive electrode mixture paste may also be applied to the surface of a resin film, dried to form the positive electrode active material layer 2, and the resin film may be released to produce the positive electrode layer. In this case, it is preferable to apply a release agent to the resin film in advance.

(Method for manufacturing solid electrolyte layer)
The solid electrolyte layer 3 can be prepared, for example, through a process of pressing a solid electrolyte. Alternatively, the solid electrolyte layer 3 can be prepared through a process of applying a solid electrolyte paste prepared by dispersing a solid electrolyte in a solvent to the surface of a substrate or an electrode. The solvent used in this case is not particularly limited and may be appropriately selected depending on the properties of the binder and the solid electrolyte. The thickness of the solid electrolyte layer 3 varies greatly depending on the configuration of the battery, but is preferably, for example, 0.1 μm to 1 mm, and more preferably 1 μm to 100 μm.

(Method of manufacturing the negative electrode layer)
The negative electrode layer can be prepared, for example, by dispersing the negative electrode active material or the like in a solvent using an ultrasonic dispersing device or the like to prepare a negative electrode mixture paste, which is then applied to the surface of the negative electrode current collector 5, and then dried. The solvent used in this case is not particularly limited, and may be appropriately selected according to the properties of the negative electrode active material or the like. The thickness of the negative electrode layer is preferably, for example, 0.1 μm or more and 1 mm or less, and more preferably 1 μm or more and 100 μm or less. The negative electrode can be prepared through a pressing process. The negative electrode layer may be manufactured by applying the negative electrode mixture paste to the surface of a resin film, drying it to form a negative electrode active material layer 4, and releasing the resin film. In this case, it is preferable to apply a release agent to the resin film in advance.

(Method for manufacturing laminate)
In this embodiment, for example, the process includes a step of stacking the above-mentioned positive electrode layer, the solid electrolyte layer 3, and the negative electrode layer in this order to fabricate the laminate 11. A known method can be adopted as the stacking method. In addition, at this time, a step of pressing the fabricated laminate 11 may be performed.

By including a process of pressing the laminate 11, the adhesion of the laminate 11 is improved. The pressing means can be a common method such as uniaxial or biaxial pressing or roll pressing. It is preferable to apply pressure when pressing until the interfaces of the layers are bonded and intimately bonded.

(Method of manufacturing a solid-state battery)
The solid-state battery 101 according to this embodiment includes, for example, a plurality of conductive rigid bodies 6 and a plurality of laminates 11, and is fabricated by stacking the laminates 11 while sandwiched between the conductive rigid bodies 6, and then pressing them under high pressure. As a pressing means, a general method such as a uniaxial or biaxial press or a roll press can be used. It is preferable to apply pressure when pressing until the conductive rigid bodies 6 and the laminates 11 are in a dense state.

The solid-state battery 101 according to this embodiment has the following advantages.
That is, in the solid-state battery 101 according to the present embodiment, the laminates 11 and the conductive rigid bodies 6 are alternately stacked, and the conductive rigid bodies 6 are disposed on both outermost sides in the stacking direction. As a result, when the laminates 11 are stacked and then pressed, all the laminates 11 are sandwiched between the conductive rigid bodies 6, so that it is possible to suppress short-circuiting and destruction due to rolling in the electrode layers of the individual laminates 11. Here, FIG. 5 is an exploded cross-sectional view of a conventional solid-state battery 201. In the conventional solid-state battery 201, the laminates 21 are continuously disposed in the center in the stacking direction, and both sides of the laminates 11 are not sandwiched between the conductive rigid bodies 6, so that short-circuiting and destruction due to rolling occur in the electrode layers, but this can be suppressed according to the present embodiment.

Second Embodiment
Next, a second embodiment of the present invention will be described with reference to the drawings. Descriptions of configurations common to the first embodiment will be omitted as appropriate. However, the embodiment shown below is merely an example of the present embodiment, and the present invention is not limited to the following.

[Solid battery]
2 is a cross-sectional view showing the configuration of a solid-state battery 102 according to a second embodiment of the present invention. The solid-state battery 102 according to this embodiment is different from the solid-state battery 101 according to the first embodiment in that it includes an insulating spacer 7 on the outer side in the planar direction of the positive electrode active material layer 2, but is otherwise similar in configuration to the first embodiment.

(Insulating spacer 7)
The insulating spacer 7 is disposed on the outer side of the surface direction of the positive electrode active material layer 2 of the laminate 12, and electrically insulates between the positive electrode layer and the negative electrode layer of the laminate 12. The insulating spacer 7 is not particularly limited as long as it is an insulating material, and a known material can be applied. By disposing the insulating spacer 7 on the outer side of the surface direction of the positive electrode layer constituting the laminate 12, it is possible to more reliably suppress short circuits caused by destruction of the electrode layer that occur when a solid battery 102 is manufactured by stacking a plurality of laminates 12 and then pressing them under high pressure. The insulating spacer 7 can be disposed by inserting it between the solid electrolyte layer 3 and the positive electrode active material layer 2 from the outer side of the surface direction after the laminate 12 is manufactured by the same manufacturing method as the manufacturing method of the laminate 11 described in the first embodiment. Alternatively, the insulating spacer 7 can be formed by applying a paste containing the constituent material of the insulating spacer 7 and drying it, similar to the formation of the positive electrode active material layer 2.

The solid-state battery 102 according to this embodiment has the same effects as the first embodiment. In addition, since the insulating spacer 7 is provided on the outer side of the surface direction of the positive electrode active material layer 2, short-circuiting of the electrode layer due to rolling can be more reliably suppressed when the laminate 12 is stacked and then pressed under high pressure.

Third Embodiment
Next, a third embodiment of the present invention will be described with reference to the drawings. Descriptions of configurations common to the first and second embodiments will be omitted as appropriate. However, the embodiment shown below is merely an example of the present embodiment, and the present invention is not limited to the following.

[Solid battery]
3 is a cross-sectional view showing the configuration of a solid-state battery 103 according to a third embodiment of the present invention. The solid-state battery 103 according to this embodiment differs from the solid-state battery 101 according to the first embodiment in that it includes an assembly 13 formed by stacking a pair of laminates having the same configuration as the laminate 11 of the first embodiment such that the positive electrode current collectors 1 are in contact with each other, and that the assembly 13 and the conductive rigid bodies 6 are stacked alternately. The other configurations are the same as those of the first embodiment.

(aggregate)
As described above, the assembly 13 according to this embodiment is configured by stacking a pair of laminates, each of which is made up of a positive electrode collector 1, a positive electrode active material layer 2, a solid electrolyte layer 3, a negative electrode active material layer 4, and a negative electrode collector 5 stacked in this order, so that the positive electrode collectors 1 are in contact with each other. The assembly 13 is produced by joining the positive electrode collectors of the pair of laminates described above, and a conventionally known method can be used as the joining method.

According to the solid-state battery 103 of this embodiment, the same effect as that of the first embodiment is achieved. Here, FIG. 6 is an exploded cross-sectional view of a conventional solid-state battery 202. In the conventional solid-state battery 202, the assembly 22 is continuously arranged in the center of the stacking direction, and both sides of the assembly 22 are not sandwiched by the conductive rigid body 6, so that a short circuit or destruction occurs in the electrode layer due to rolling, but this can be suppressed according to this embodiment. In addition, according to this embodiment, a pair of laminates in which a positive electrode collector 1, a positive electrode active material layer 2, a solid electrolyte layer 3, a negative electrode active material layer 4, and a negative electrode collector 5 are stacked in this order, and the positive electrode collectors 1 are stacked so that they are in contact with each other to form an assembly 13, so that high output due to direct connection of the electrode layers can be expected.

Fourth Embodiment
Next, a fourth embodiment of the present invention will be described with reference to the drawings. Descriptions of configurations common to the first to third embodiments will be omitted as appropriate. However, the embodiment shown below is merely an example of the present embodiment, and the present invention is not limited to the following.

[Solid battery]
4 is a cross-sectional view showing the configuration of a solid-state battery 104 according to a fourth embodiment of the present invention. The solid-state battery 104 according to this embodiment differs from the solid-state battery 103 according to the third embodiment in that it includes an insulating spacer 7 on the outer side in the planar direction of the positive electrode active material layer 2, but the other configurations are the same as those of the third embodiment. The insulating spacer 7 has the same configuration as the insulating spacer 7 of the second embodiment.

The solid-state battery 104 according to this embodiment enhances the effects of the first to third embodiments.

The present invention is not limited to the above-described embodiment, and any modifications or improvements that can achieve the object of the present invention are included in the present invention.

REFERENCE SIGNS LIST 1 Positive electrode current collector 2 Positive electrode active material layer 3 Solid electrolyte layer 4 Negative electrode active material layer 5 Negative electrode current collector 6 Conductive rigid body 7 Insulating spacer 11, 12, 21, 22 Laminate 13, 14 Assembly 101, 102, 103, 104 Solid-state battery

Claims (3)

a laminate including one positive electrode current collector, one positive electrode active material layer, one solid electrolyte layer, one negative electrode active material layer, and one negative electrode current collector, the laminate being configured by stacking the positive electrode current collector, the positive electrode active material layer, the solid electrolyte layer, the negative electrode active material layer, and the negative electrode current collector in this order;
a conductive metal material;
The laminate and the conductive metal material are alternately laminated, and the conductive metal material is disposed on both outermost sides in the lamination direction;
A solid-state battery, wherein the conductive metal material has a length in a planar direction greater than a length of an electrode layer of a single laminate that faces the conductive metal material. The solid-state battery according to claim 1, wherein the end of the positive electrode active material layer in the planar direction is disposed on the inner side in the planar direction than the end of the adjacent solid electrolyte layer in the planar direction. The solid-state battery according to claim 1 or 2, further comprising an insulating spacer provided on the outer side of the positive electrode active material layer in the planar direction.

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